Single-injection syringe

ABSTRACT

Inside a syringe (1) slides a plunger (2) which bears a joint (4) sliding sealingly over the internal wall of the syringe. The flexible membrane (6) of the joint (4) fixed to the end of the plunger (2) bears a closing component (25, 27) which follows the movement of deformation or displacement of the membrane through the effect of the pressure built up during the injection stage, but which is retained by immobilizing strips (17) in a position in which it opens the orifice, breaking the seal between the top and the bottom of the joint, as soon as the membrane returns to its initial position.

FIELD OF THE INVENTION

The present invention relates to a disposable syringe, that is one thatcan be used only once, and relates more precisely to a device thatrenders the sealing joint inoperative after a first injection.

BACKGROUND OF THE INVENTION

In the field of therapeutics, the use of syringes for injecting fluidsinto tissues or natural cavities in the body is extremely widespread. Asyringe is known to be composed essentially of a cylindrical barrel inwhich a plunger slides, a body whose base bears a nozzle of a suitableshape to which can be fitted a hollow needle, for example a needle madeof steel or nickel, the barrel thus forming a reservoir for the fluid tobe injected. The structure or composition of the plunger can varyaccording to the model. It is, in any case, provided at one of its endswith a joint to ensure sealing with the barrel of the syringe and, atits other end, which is always external to the barrel of the syringe, aplunger head to facilitate its handling. This classical syringe makes itpossible to perform in the habitual manner the operations required foran injection as commonly practised, that is in the first place,detaching the joint at the bottom of the syringe and then, by applyingtraction to the plunger to extract it from the barrel of the syringe,drawing in a certain quantity of fluid. Then, with the syringe ininverted position, that is with the needle pointing upwards, a slightpressure on the plunger causes any air remaining in the reservoir to bedischarged, this operation possibly being followed by the drawing in ofa complementary quantity of fluid and again the essential discharge ofthe air.

Before injection properly speaking, slight re-aspiration is practisedafter insertion for checking purposes.

There are known disposable syringes used for vaccinations which arepre-filled in the laboratory and with which it is no longer possible todraw in fluid after the injection. However, as most syringes used arenot pre-filled and since it has to be possible for the to and fromovements of the plunger to be performed for the operations describedabove, or for manipulations in an empty condition, it is not possible toadopt this system.

SUMMARY OF THE INVENTION

One object of the present invention is thus to provide a deviceadaptable to any syringe, which permits the performance of all theoperations necessary for a complete injection and thus including the toand fro movements of the plunger or its manipulation in an emptycondition as described above, but which strictly precludes re-use for asecond injection, the device rendering the sealing joint inoperativeafter the first injection by making use of the action of the pressureexerted by the fluid, during injection, on a flexible part of the jointto detach the joint from its driving plunger, or to destroy its functionas a sealing member.

The invention thus relates to a disposable syringe comprising acylindrical syringe barrel to the base of which can be fixed differentsorts of sampling and/or injection needles, as well as a plunger slidinginside the syringe barrel and whose end bears a joint the slidessealingly over the internal wall of the syringe, a syringe in which thejoint comprises at least one member capable of being deformed ordisplaced from its position of equilibrium through the action of thepressure exerted by the fluid contained in the syringe at the time ofthe injection stage, the sliding plunger being associated with the jointvia components that react to the deformation or the displacement of themember and which render the joint inoperative for the purposes ofrefilling after the injection.

According to the special features of the invention, the joint is ahollow cylindrical component whose lower face is formed by a flexiblemembrane that constitutes the deformable member and which ensuressealing between the syringe barrel and the chamber inside the joint andwhose annularly shaped upper portion bears against the plunger, whichplunger extends, through the orifice in the annular portion of thejoint, by an axial rod having a diameter less than that of the orificeand ending in a head forming a shoulder with the rod.

According to one special feature of the invention, the flexible membraneor the displaceable member has an orifice that is normally tightlyclosed by a closing component which follows the movement of deformationor displacement of the membrane or of the member through the effect ofthe pressure built up during the injection stage, but which is retainedby an immobilizing device in a position in which it opens the orifice,breaking the seal between the top and bottom of the joint, as soon asthe membrane or the member returns to its initial position.

DESCRIPTION OF THE DRAWINGS

Other special features and advantages of the invention will emerge as aresult of reading the following description of examples of embodimentswith reference to the annexed drawings, wherein:

FIG. 1 is a schematic view in elevation of an equipped syringe in a restposition;

FIG. 2 shows the same syringe during an injection stage;

FIGS. 3 and 4 show another form of embodiment, also in two positions;

FIGS. 5 and 6 show another variant of a syringe equipped with a devicefor detaching the joint in a rest position and in an injection position.

FIGS. 7 and 8 show a schematic elevation view of a syringe equipped witha device for perforating the joint, in a rest position and in aninjection position;

FIG. 9 shows an alternative form of embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The syringe represented in FIG. 1 is composed essentially of acylindrical syringe barrel 1 to the base of which is fixed a sampling orinjection needle 3, a plunger 2 sliding inside the syringe barrel and asealing joint 4 mounted on the end of the plunger and sliding sealinglyover the internal wall of the syringe. The plunger cannot be withdrawnfrom the barrel of syringe 1 because of a non-return device 16 whichprevents any interference with the device. The sealing joint 4 takes theform of a hollow cylindrical component whose external wall is providedwith integrally moulded ribs 5, forming a seal on the internal wall ofsyringe barrel 1. The lower face of the joint, opposite the orifice inthe syringe barrel, forms a flexible membrane 6 whose thickness isreduced in relation to the rest, a membrane which, in the position ofequilibrium, is substantially horizontal and ensures sealing between thesyringe barrel and a chamber 21 internal to the joint. On the otherside, the upper portion 7 of the annularly shaped joint, bearing againsta shoulder 9 of the plunger, is thicker and is provided with a centralorifice 28. The lower face of this upper portion 7 of the joint bearsagainst a shoulder 19 projecting from a hollow cylindrical rod 10 whichprolongs the plunger 2 and extends inside the joint. Joint 4 is thusmade integral with the plunger 2. Inside the hollow rod 10 is placed aclosing component 25, having a generally elongated shape, and whosecross-section is cylindrical or star-shaped. This component is able tomove with a slight amount of clearance inside the shaft constituted byrod 10 which further bears an internal shoulder 26 delimiting within therod a lower shaft having a smaller cross-section than the upper shaft atthe annular portion 7. The shoulder could also be a boss covering orotherwise the entire circumference of the shaft. The closing component25 ends towards the bottom in a closing head 27 which closes a smallorifice 28 provided in the membrane 6. On its upper portion, closingportion 25 carries elastic strips 17 held folded back when they areapplied against the internal wall of rod 10, and which play the part ofa non-return member, as we shall see later. It will be noted that rod 10is traversed by ports 20 placing the internal chamber 21 of the joint 4in communication with the internal shaft of the rod and, thereby, viaports 22 provided in the plunger, with the syringe above the shoulder ofthe plunger. The position represented in the FIG. 1 corresponds to thepre-injection stage. Head 27 of the closing component 25 sealinglycloses the membrane 6, following its movement.

Directly the injection stage commences, as represented in FIG. 2.Through the effect of the pressure built up, membrane 6 is deformed fromthe position shown in dashed lines to the position shown in solid lines.The closing component 25 follows this movement and the elastic strips 17then escape from the lower shaft and spread out in the upper well. Theywill then be immobilized by the shoulder 26, making any return of thecomponent to its initial position impossible. This non-return functiononly takes effect if the pressure in the reservoir has reached apredetermined maximum value, the displacement of the closing componentremaining reversible for all values lower than the said pressure.Following injection, the joint 4 remains integral with the plunger but,as the deformed portion of the membrane 6 is no longer subjected to thepositive pressure, it has regained its initial shape. However, theclosing head 27 remains at a distance from the membrane and orifice 28is disengaged. Chamber 21 is connected to atmosphere by the ports 22provided in plunger 2, and by ports 20, and also communicates with thebottom of the syringe via orifice 28. The seal is thus broken betweenthe top and the bottom of the joint. Thus, it becomes impossible to fillthe injection device by drawing in fluid or through the action of apressurized fluid, or to perform an injection.

According to another form of embodiment, not shown, it can becontemplated that the bottom 6 remains rigid but that it is the sidewalls of the joint 4, below its annular portion 7, that are deformed andfold at the time of the injection stage and displace the base of thejoint and the closing component upwards.

According to yet another form of embodiment, not shown, the closingportion is not fitted with non-return elastic strips 17 but is stuck inthe top position against the plunger by means of an adhesive or asuitable glue located on the plunger and/or the component.

FIGS. 3 and 4 show yet another form of embodiment, again in the twohabitual operating stages. This time, the closing component 25 isconstituted by a dome-shaped strip 31 the concavity of which is directeddownwards, in the same direction as that of the undeformed membrane 6 ofthe joint 4 inside which it is maintained. The dome-shaped strip 31bears in its center a closing head 27 which also cooperates with orifice28. In the initial stage (FIG. 3), strip 31 is in a cambered position,as shown, in which orifice 28 is closed. At the time of the injectionstage illustrated in FIG. 4, the positive pressure in the syringe issufficient for deformation of the membrane 6 to push the dome-shapedstrip 31 upwards. Its concavity then changes direction and it remains inthis position. When the membrane regains its initial position, at theend of injection, orifice 28 is no longer closed by closing head 27since the strip has remained cambered in the upper position. It will benoted that the friction between the head 27 and the edges of themembrane around its orifice 28 is insufficient to return dome-shapedstrip 31 from the position shown in FIG. 4 to that shown in FIG. 3merely through the traction of membrane 6 returning to its initialposition.

According to another form of embodiment, not shown, the dome-shapedstrip, instead of being associated with the joint 4, could be associatedwith a displaceable rigid member.

In the case of the variants in FIGS. 3 and 4, operation and the resultobtained are the same as in the case described with reference to FIGS. 1and 2.

The invention has been described with reference to a joint 4 that takesthe form of a hollow cylindrical component whose external wall isprovided with integrally moulded ribs forming a seal on the internalwall of syringe barrel 1, and whose lower portion is a deformablemembrane 6. The invention can also be considered as applying to asyringe plunger fitted with at least an added joint or profiled so as toact as a joint itself, which would be equipped with a deformable memberplaying the same part as that described above, or with a displaceablecomponent instead of providing for displacement of the bottom of thejoint, described earlier, through the effect of pressure.

To improve non-reutilization security yet further, it can beadvantageous to provide for an area of weakness, for example at closinghead 27. Any attempt to restore the closing component 25 to its initialposition by traction would result in rupture between the head and theclosing component.

We shall now describe, with reference to FIGS. 5 and 6, another form ofembodiment in which, this time, the membrane 6 of joint 4 is no longerperforated and remains tight but contains a device that detaches thejoint from the plunger.

It can be see from FIG. 5, in which the same reference numbers are usedfor the same components as those described in connection with FIG. 1,that axial rod 10 which extends the plunger has a portion 10a with adiameter substantially less than the diameter of orifice 8, at theorifice, and that the rod ends in a conical head 11 with a largerdiameter forming a shoulder 19 with the rod, a conical head whose tip isorientated towards the membrane 6 of the joint, the diameter of theshoulder remaining less than the diameter of orifice 8. Rod 10 has aneck 12 between shoulder 9 and conical head 11, the head being conicalto enable the plunger to be mounted more easily on a clamp. Portion 10bof the rod between the neck and the conical portion has been bevelled topresent a slightly conical profile, as seen from FIG. 5. An elasticclamp 13 formed by arms 14 which turn inwards by jaws 15 towards thecenter of the syringe is arranged inside joint 4 and caps conical head11. It is shown spread in FIG. 5 and its jaws 15 whose ends have aconical profile corresponding to that of portion 10b bear againstportion 10b of rod 10 and against the upper shoulder of the conicalportion.

If a downward pressure is applied to plunger 2, shoulder 9 pushesagainst the upper face 7 of the joint. If, on the other hand, upwardtraction is applied to the plunger, starting from the position shown inFIG. 5, for example to ensure that fluid is drawn into the syringe, thejaws 15 of the clamp held apart by portion 10b by a distance greaterthan the diameter of orifice 8 abut against the annular portion 7 of thejoint and enable the latter to be driven together with the plunger. Theway in which the plunger and the joint are thus rendered integralpermits the operations prior to injection mentioned previously.

FIG. 6 illustrates the final stage of fluid injection while the plunger2 is descending towards the bottom of syringe 1. At that moment, thepressure of the fluid in the syringe, through the effect of the thrustof joint 4, causes deformation of the membrane 6, which bulges towardsthe interior of the joint 4. The membrane then bears against clamp 13,displacing it upwards until the jaws 15 escape from portion 10b of therod and, as a result of the elasticity of arms 14, close up in groove12. The spread of the clamp is then reduced to a size that is less thanthat of orifice 8 and it will then be appreciated that, followinginjection, if it is attempted to draw the plunger out of the syringe,the clamp will pass through orifice 8 and the joint will remain at thebottom of the syringe. It will be noted that, even if this detachmentfrom the joint through withdrawal of the clamp has occurred at the startof the depression stroke of the plunger, injection will not be adverselyaffected thereby and will be able to continue normally thanks to thethrust of shoulder 9 against the joint. At the end of the stroke,conical head 11 of plunger 2, through its action on membrane 6, willpress the latter against the bottom of the syringe, enabling all thefluid to be injected. The deformation of the joint in this final stageis of no importance since, in any case, the clamp will no longer be ableto cooperate with annular portion 7 of the joint, which will remain atthe bottom.

If, for any reason, the jaws of clamp 13 should fail to escape fromportion 10b of the rod, as a result of the pressure, detachment wouldnonetheless occur when the clamp came into abutment through the membranewith the bottom of the syringe, at the end of the plunger travel stroke.

The clamp which can be seen in FIGS. 5 and 6 can have a profile thatdiffers from that shown and, in particular, a lower face, from whichextend arms 14, that is substantially larger, to avoid sliding onmembrane 6 and to cooperate more easily therewith at the end ofinjection.

There will now be described yet another form of embodiment in whichmembrane 6 is impervious, as in the above cases, and not provided withan orifice, but in which, on the other hand, it can be perforated.

This variant is described with reference to FIGS. 7 and 8, which showthat conical head 11, still integral with plunger 2 via rod 10, andhoused inside joint 4, is larger in size. Its shoulder 19 in relation tothe rod abuts against the annular lower portion 7 of joint 4, cappingorifice 8. This annular portion 7 of the joint is thus pinched betweenshoulder 9 and shoulder 19; the joint and the plunger are thus renderedinseparable. As in the cases illustrated in FIGS. 5 to 6; conical head11 is traversed by ports 20 placing the internal chamber 21 of joint 4in communication with orifice 8. Other ports 22 are provided in theplunger itself so that there is free communication of air betweenchamber 21 and the syringe, above shoulder 9 of the plunger. Inaddition, conical head 11 is provided at its end with a point 23orientated towards membrane 6, a point that could also be replaced by acutting part of any shape.

In the position represented in FIG. 7, which corresponds to a stage inoperations that is preliminary to injection properly speaking, membrane6 occupies a position of equilibrium that holds it away from point 23.Once the injection stage takes place and the pressure of the fluidbecomes sufficient to deform membrane 6, the latter is pressed hardagainst point 23 and is perforated (FIG. 8). Nonetheless, injection canbe pursued normally as the point blocks the perforation and prevents thefluid from entering chamber 21. At the end of injection, joint 4 remainsintegral with the plunger, as seen earlier, but if it is attempted todraw in fluid again with a view to another injection, the perforation ofmembrane 6 will make this operation impossible. Air will, in fact, havebeen able to pass through ports 20, 22 and the perforation, and topenetrate to the bottom of the syringe, definitively preventing theapplication of any negative air pressure and any possibility of drawingin fluid. Non-return device 16 or any other system obstructing thesyringe on the upper portion but allowing the plunger to slide alsoprevents any interference with the syringe in all the cases described.

According to yet another form of embodiment, illustrated in FIG. 9,clamp 13, used in accordance with the third form of embodiment inconformity with FIGS. 5 and 6, has on its lower portion a protuberance24 which can have the shape of a tip with a rounded end. When the jointis mounted, steps are taken to ensure that the protuberance 24 is on theother side of membrane 6 in relation to the clamp, the tip of theprotuberance passing through a central hole provided on the membrane.

The clamp and the membrane are thus rendered integral.

Operation is identical with that described in connection with the formof embodiment of FIGS. 5 and 6, that is the bulging of membrane 6 at thetime of injection pushes upwards clamp 13 the jaws of which could closeup in groove 12. If a user attempts to extract plunger 2, the driving ofclamp 13 will draw out protuberance 24, unblocking the hole provided onthe membrane, and there will remain this hole in joint 4 which willrepresent, in addition to the joint and the plunger being detached fromone another, an additional deterioration of the joint rendering itinoperative. It will be noted that the protuberance can be withdrawnthrough the membrane owing to forces of friction of the joint in thesyringe barrel being greater than the force of retention of theprotuberance by the hole in the membrane. We thus come back to the casesillustrated in FIGS. 1 to 4.

A supplementary advantage of this variant is that the clamp is thusperfectly positioned in relation to the joint.

The devices thus described can be adapted to all types of syrings. Apartfrom the fact that they are perfectly efficient and strictly preventreutilization of the syringes equipped therewith, they are simple tomake and thus inexpensive.

We claim:
 1. A disposable syringe comprising:a cylindrical syringebarrel; means for attaching a needle at one end of said syringe barrel;a plunger mounted for movement toward and away from said one end of saidsyringe barrel; a hollow member mounted at one end of said plunger forsliding movement internally of said syringe barrel, said hollow memberincluding a deformable element disposed between said plunger and saidone end of said syringe barrel, said deformable element is disposed inone position and capable of displacement to a second position uponmovement of said plunger toward said one end of said syringe barrel,said deformable element having an orifice; at least one external rib onsaid hollow member providing a seal between said hollow member and aninternal surface of said syringe barrel; and closing means locatedbetween said plunger and said deformable element of said hollow member,said closing means closing said orifice when said deformable element isinitially in said one position, and movable to a second position inresponse to movement of said deformable element to said second positionto prevent a second aspiration of a liquid following a first aspirationof liquid by movement of said plunger away from said one end of saidsyringe barrel whereby said closing means disengages from and opens saidorifice upon corresponding displacement of said deformable element fromsaid second position.
 2. A disposable syringe comprising:a cylindricalsyringe barrel; means for attaching a needle at one end of said syringebarrel; a plunger mounted for movement toward and away from said one endof said syringe barrel; a hollow cylindrical member mounted at one endof said plunger for sliding movement internally of said syringe barrel,said hollow member including an annular shaped upper portion which bearsagainst said plunger and a flexible membrane forming a surface facingsaid one end of said syringe barrel and disposed between said plungerand said one end of said syringe barrel, said flexible membrane isdisposed in one position and capable of displacement to a secondposition upon movement of said plunger toward said one end of saidsyringe barrel; an orifice in said flexible membrane; at least oneexternal rib on said hollow member providing a seal between said hollowmember and an internal surface of said syringe barrel; and closing meanslocated between said plunger and said flexible membrane of said hollowmember, said closing means closing said orifice when said flexiblemembrane is initially in said one position, and movable to a secondposition in response to movement of said flexible membrane to saidsecond position to prevent a second aspiration of a liquid following afirst aspiration of liquid by movement of said plunger away from saidone end of said syringe barrel, whereby said closing means opens saidorifice upon corresponding displacement of said flexible membrane fromsaid second position.
 3. A disposable syringe according to claim 2,wherein the closing means follows the movement of said flexible membranethrough pressure built up at the time of injection, and said closingmeans is retained by an immobilizing means in a position in which saidclosing means opens the orifice, breaking a seal between a top andbottom of the hollow member, as soon as the flexible membrane returns toan initial position.
 4. A disposable syringe according to claim 3,wherein the closing means is mounted inside a hollow rod bearing aninternal shoulder which extends the plunger and includes a closing headat the end of said hollow rod which closes the orifice provided in theflexible membrane.
 5. A disposable syringe according to claim 3, whereinthe immobilizing means for immobilizing the closing means areconstituted by elastic strips borne by said closing means and foldedback inside a hollow rod, said elastic strips gripping an internalshoulder of the hollow rod when the closing means has been displaced bydeformation of the flexible membrane.